The invention relates generally to control systems for internal combustion engines, and more particularly, concerns a powertrain output monitor for electronic throttle control-equipped vehicles.
Present powertrain output monitor techniques typically compute an estimate of engine output and compare that value to the requested engine output. Such methods typically take the form of resolving one or more engine operating parameters and comparing the estimated versus requested output value. Such operating parameters can include: engine output torque, engine output power, wheel torque, wheel power, and wheel acceleration. The requested output is typically a function of driver demand as measured by the accelerator pedal position, combined with internally automated demands such as idle speed control and catalyst heating.
Due to the complex nature of determining estimated and requested engine output as a function of one or more engine operating characteristics and driver inputs, diagnostics based upon such monitoring techniques are inherently complex. Therefore, there exists a need for a simplified method of monitoring the powertrain control system.
In cases where engines are designed for optimum fuel efficiency (i.e., variable valve timing, lean burn, direct injected spark-ignited, high EGR rates), fuel is the variable most directly related to engine torque (fuel quantity injected per stroke) or power (fuel rate). Accordingly, there is a need for a powertrain output monitoring method relating to engine fuel flow.